Abstract
We report the discovery of bulk superconductivity (SC) at 6.1 K in a quasi-one-dimensional chromium pnictide that contains double-walled subnanotubes with face-sharing () octahedron linear chains in the inner (outer) wall. The material has a large electronic specific-heat coefficient of , indicating significantly strong electron correlations. A linear temperature dependence of resistivity in a broad temperature range from 7 to 300 K is observed, which suggests non-Fermi liquid behavior of the material. Unconventional SC is preliminarily manifested by the estimated upper critical field exceeding the Pauli limit by a factor of 3–4. The title compound represents a rare example that possibly unconventional SC emerges in a quasi-1D system with strong electron correlations.
- Received 13 January 2015
DOI:https://doi.org/10.1103/PhysRevX.5.011013
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Published by the American Physical Society
Popular Summary
Explorations of novel superconductors have been at the forefront of over 100 years of superconductivity research. The discovery of high-temperature superconductivity in quasi-two-dimensional copper oxides in the 1980s led to a paradigm that quasi-two-dimensional systems with strongly correlated electrons may host unconventional superconductivity. Indeed, unconventional superconductivity has been discovered in a few classes of layered materials containing -block elements, such as iron pnictides. Observations of superconductivity in quasi-one-dimensional materials with strongly interacting electrons, however, are rare and are of great interest given the relative simplicity of one dimension.
We report the discovery of bulk superconductivity at 6.1 K in an alkali-metal chromium pnictide, , with significant electron correlations. We study the crystalline structure of this material (bond lengths and bond angles) using x-ray diffraction and find that the hexagonal lattice contains quasi-one-dimensional double-walled subnanotubes (about 0.58 nm in outer diameter) with face-sharing octahedron linear chains in the inner and outer walls. The material indeed bears significantly strong electron correlations, as manifested by a large electronic specific-heat coefficient. We observe sharp superconductivity transitions at 6.1 K, below which resistivity drops to zero, the external magnetic field is expelled, and the specific heat shows a jump. Furthermore, the signature of non-Fermi liquid appears as a linear temperature dependence of resistivity in a broad temperature range (7–300 K). Unconventional superconductivity is additionally evident based on the high upper critical field exceeding the Pauli limit.
Our findings highlight a rare example of superconductivity in a quasi-one-dimensional material and stimulate further explorations of new superconductors in related systems. We expect that our results will additionally expand research domains in quasi-one-dimensional physics and unconventional superconductivity.
